JP2011097179A - Imaging device and image analysis computer program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To precisely specify the position of a pixel for receiving light incident on the center of a microlens through an imaging optical system so as to improve the precision of image composition, focus detection and focus adjustment. <P>SOLUTION: The imaging device includes: a microlens array composed of a plurality of microlenses; a light receiving element array composed of a plurality of light receiving elements for receiving a luminous flux from an optical system through the microlens array and outputting a light receiving signal; an image generating means for generating a first image including an image corresponding to the contour of the plurality of microlenses on the basis of the light receiving signal obtained by the plurality of light receiving elements; and an operating means for calculating the position of an image coincident with a second image corresponding to the contour of the microlenses in the first image. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an imaging apparatus and an image analysis computer program.

  There is known an imaging apparatus that synthesizes an image focused on an arbitrary image plane from data obtained by one imaging (see, for example, Patent Document 1). In the imaging apparatus disclosed in Patent Document 1, image data is synthesized based on the output value of a pixel that receives a light beam that passes through a photographing optical system and is incident on the center of a microlens.

JP 2007-4471 A

  However, the position of the pixel that receives the light incident on the center of the microlens through the photographing optical system described above is a low-accuracy image data synthesis process when the design value is used, and thus the obtained image can be out of focus. . This is because it is difficult to manufacture a microlens array in which microlenses are arranged and an image pickup element in which pixels are arranged so as to be precisely aligned. That is, there is a problem that the position of the pixel that receives the light beam that passes through the photographing optical system and enters the center of the microlens cannot be accurately specified.

An imaging apparatus according to a first aspect of the present invention includes a microlens array in which a plurality of microlenses are arranged, and a plurality of light receiving elements that receive a light beam from an optical system and output a light reception signal through the microlens array. Based on the arrayed light receiving element array, and light reception signals obtained by the plurality of light receiving elements, an image generating means for generating a first image including an image corresponding to the outline of the plurality of microlenses, An arithmetic means for obtaining a position of an image corresponding to the second image corresponding to the outline of the microlens is provided.
An image analysis computer program according to a ninth aspect of the present invention is a photographic image data generated in an imaging apparatus including a microlens array in which a plurality of microlenses are arranged and a light receiving element array in which a plurality of light receiving elements are arranged. An image analysis computer program used for image analysis for generating a first image data including images corresponding to the outlines of a plurality of microlenses based on light reception signals obtained by a plurality of light receiving elements; A calculation instruction for obtaining a position of an image corresponding to the second image corresponding to the outline of the microlens among the first image is provided.

  According to the present invention, the accuracy of image synthesis and focus detection and focus adjustment is improved.

It is a figure explaining the structure of the camera by 1st Embodiment. It is a flowchart showing the detail of operation | movement of a main control part. It is a front view of an image sensor on which a subject image is projected. It is the figure which expanded the partial area | region of the image pick-up element. It is a figure showing the result of having performed the edge extraction process with the image data of the partial area | region shown by FIG. It is a figure which shows the template image used for the pattern matching for calculating the pupil projection center position in FIG. It is a flowchart which shows the detail of the pupil center projection position determination which a main control part performs in step S210 in FIG. It is a figure which shows the point which plotted the pupil projection center position for the sampling number on the coordinate plane by x-axis and i-axis, and its regression line. In 2nd Embodiment, it is a flowchart which shows the detail of the pupil center projection position determination which a main control part performs in step S210 in FIG. 10 is a flowchart showing details of pupil center projection position determination executed by a main control unit in step S210 in FIG. 2 in the third embodiment. It is a figure which shows the connection structure of PC and camera by 4th Embodiment. It is a flowchart which shows the detail of the pupil center projection position determination which PC by 4th Embodiment performs according to an image analysis computer program.

--- First embodiment ---
A first embodiment in which an imaging apparatus according to the present invention is applied to a camera will be described with reference to FIGS. FIG. 1 is a diagram illustrating the configuration of a camera 1 according to this embodiment. A camera 1 shown in FIG. 1 includes a camera body 10 and a lens barrel 15 and has either or both of a focus detection function and an image composition function. The lens barrel 15 includes a photographing optical system control unit 150, a photographing lens 160, and a lens barrel memory 170. The camera body 10 includes a main control unit 100, an image sensor 110, a microlens array 120, a built-in memory 130, and a memory card 140.

  In the lens barrel 15, the photographing optical system control unit 150 adjusts the focus of the photographing lens 160 by driving the photographing lens 160 and a diaphragm (not shown) based on an instruction from the main control unit 100 of the camera body 10. The lens barrel memory 170 stores design values of the photographic optical system 160 such as a focal length or an open F value of the photographic lens 160.

  In the camera body 10, the main control unit 100 detects the focus of the photographic lens 160, and based on this, controls the focus adjustment of the photographic lens 160 in the photographic optical system control unit 150 described above, and the image sensor 110 detects the subject. Image data obtained by imaging is recorded in the memory card 140. In addition, photographing optical system attribute information is acquired from the photographing optical system control unit 150, a pupil center projection position is determined by a process described later, and is recorded in the built-in memory 130.

In FIG. 1, the distance between the photographing lens 160 and the microlens array 120 (hereinafter referred to as the pupil position) is h. The distance between adjacent microlenses constituting the microlens array 120 is d, and the focal length of each microlens is equal to the distance between the microlens array 120 and the image sensor 110 and is f. If the vertical or horizontal direction of the image pickup element was defined as x-axis, the position of the pixel receiving the light rays incident on the center of the nearest micro lens in the optical axis of the taking lens 160 and x _0, and 0 th and the microlenses Then, the position of a pixel that receives a light beam incident on the center of the i-th microlens in the x-axis direction from the microlens is defined as _xi .

  FIG. 2 is a flowchart showing details of the operation of the main control unit 100. FIG. 2A shows that the main control unit 100 determines the pupil center projection position in step S210, and based on this, performs focus detection of the photographing lens 160 to control focus adjustment in step S220. ing. For focus detection and focus adjustment control of the taking lens 160, for example, a pupil division type phase difference detection method disclosed in Japanese Patent Laid-Open No. 1-216306 is used. The determination of the pupil center projection position performed in step S210 is executed immediately after the user turns on the power of the camera 1, and the focus detection and focus adjustment control of the photographing lens 160 in step S220 are started by the user's operation. It is preferable to wait for that.

  FIG. 2B is a flowchart in a case where the main control unit 100 determines the pupil center projection position in step S210 and performs image composition in step S230 based on it. For image composition, for example, a technique disclosed in Japanese Patent Application Laid-Open No. 2007-4471 is used. The determination of the pupil center projection position performed in step S210 preferably waits for the start of image composition in step S230 while periodically repeating while the through image is displayed on the monitor (not shown) in camera 1. . Details of the pupil center projection position determination process will be described below.

  FIG. 3 is a front view of the image sensor 110 on which a subject image is projected when a flower is imaged as a subject. However, pixel drawing is omitted. Further description will be made on the partial region 300 of the image sensor including the image 350 of a part of the leaves of the flower.

  FIG. 4 is an enlarged view of a partial region 300 of the image sensor including an image 350 of a part of a leaf of a flower as a subject in FIG. In the partial area 300 of the imaging element, square imaging pixels 115 are arranged adjacent to each other. The white circular region is a projected image 125 of the pupil of the photographing optical system projected onto the light receiving surface of the image sensor 110 by a light beam that passes through the photographing optical system and enters the microlens. The center position is the pupil projection center position. The projected image 125 of the pupil is clear outside the area where the partial image 350 of the leaf is projected. A method of calculating the pupil projection center position by pattern matching will be described below with reference to an enlarged view of the partial region 300 shown in FIG.

  FIG. 5 is a diagram illustrating a result of performing the edge extraction process on the image data of the partial region 300 illustrated in FIG. The edge extraction processing is obtained by differential filter processing such as Laplacian, for example. FIG. 5 shows an example using Laplacian. In the edge extracted image 305, the contour of the projected image 125 of the pupil is extracted as a bright line. The contour of the image 350 of a part of the leaf having a smaller lightness level difference is extracted as a slightly darker line. Edge extraction is not performed on the area inside the image 350 of a part of the leaf except for the vein portion. In the area where the subject image is projected, the projected image 125 of the pupil is difficult to detect.

  FIG. 6 is a diagram showing a template image used for pattern matching for calculating the pupil projection center position in FIG. 6A to 6C are template images representing large, medium, and small circles. In pattern matching using a template image, when scanning one of the images in FIGS. 6A to 6C overlaid on FIG. 5, one pixel moves to all positions for each pixel position. The correlation value indicating the degree of coincidence at each pixel position is calculated. If a threshold value for a correlation value is determined in advance, and a pattern that starts to decrease after the correlation value increases and exceeds the threshold value is detected, the contour of the pupil projection image 125 is detected, and the pupil projection center in the projection image 125 of the pupil is detected. The position can be calculated. Alternatively, since the contour of the pupil projection image 125 is estimated to exist at the position showing the highest correlation value, the pupil projection center position in the projection image 125 of the pupil is calculated based on the position data. It is also good.

  The template images shown in FIGS. 6A to 6C are recorded in advance in the built-in memory 130, and which image is used is selected based on photographing optical system attribute information such as the F value of the photographing lens 160. . This is because the size of the pupil projection image 125 (hereinafter referred to as the pupil diameter) depends on the aperture diameter and the focal length of the photographic lens 160. The main control unit 100 acquires the photographing optical system attribute information from the photographing optical system control unit 150. The correlation value calculated by pattern matching is calculated by using a technique described as a conventional technique in, for example, Japanese Patent Application Laid-Open No. 9-102039.

  In the above-described pattern matching, it is only necessary to obtain pupil projection center positions for a predetermined number of samplings. This is because the remaining pupil projection center positions are all determined by specifying an arithmetic expression to be estimated based on the obtained pupil projection center positions for a predetermined number of samplings, as will be described later. In FIG. 3, after performing the edge extraction process, the pupil projection center positions for a predetermined number of samplings may be acquired in descending order of the correlation value. They are highly likely to have been obtained by the above-described pattern matching on the data extracted completely without the outline of the pupil projection image 125 being missing, and the pupil projection center position can be calculated with high accuracy.

  In FIG. 5, the contour of the image 350 of a part of the leaf is extracted as a slightly dark line, but in order to improve pattern matching accuracy, for example, only the contour of the pupil projection image 125 is extracted by binarization processing. Then, the pattern matching described above may be performed.

  FIG. 7 is a flowchart showing details of pupil center projection position determination executed by the main control unit 100 in step S210 in FIGS. 2 (a) and 2 (b). In step S710, the imaging device 100 is controlled to image the subject. In step S720, the edge extraction process described above is performed. In step S730, photographing optical system attribute information such as the F value of the photographing lens 160 is acquired from the photographing optical system control unit 150. This may be performed before step S710 is executed.

  In step S740, a suitable template image is selected based on the photographing optical system attribute information. As a result of performing pattern matching in step S750, the pupil projection center position is calculated in step S760. By the determination process in step S770, the correlation value is calculated while moving the template image one pixel at a time until the pupil projection center positions for the number of samplings are acquired, and the processes in step S750 and step S760 are repeated.

  When the pupil projection center positions for the number of samplings are acquired, an arithmetic expression for the pupil projection center position, which will be described later, is specified in step S780. Using this, when all pupil projection center positions are determined and recorded in the built-in memory 130 in step S790, the processing executed by the main control unit 100 returns to FIG. 2 (a) or (b).

The specification of the calculation formula for the pupil projection center position in step S780 shown in FIG. 7 will be described. From FIG. 1, the position of a pixel that receives a light beam incident on the center of the i-th microlens is denoted by _xi, and the position of a pixel that receives a light beam incident on the center of the microlens closest to the optical axis of the photographing lens 160 and x _0, and the pupil position h, and the adjacent spacing d of the micro lens, between the focal length f of the microlens, holds the relationship expressed in equation (1).

Equation (2) is derived from Equation (1).

The pupil projection center positions for the number of samplings obtained above correspond to x _i , that is, if they are plotted on the coordinate plane by the x-axis and i-axis, they should return to the straight line represented by Equation (2). is there. FIG. 8 shows points obtained by plotting the pupil projection center positions for the number of samplings on the coordinate plane by the x-axis and the i-axis and the regression line represented by the equation (2). Based on the acquired pupil projection center positions for the number of samplings described above, the slope d (1 + f / h) of the straight line represented by equation (2) is obtained by the least square method represented by equation (3).

The x-intercept x ₀ (1 + f / h) of the regression line represented by the formula (2) is obtained from the formula (2) and the formula (3) according to the formula (4).

Since the adjacent distance d of the microlenses and the focal length f of the microlens are known values as design values in advance, the pupil position h can be obtained from Expression (3). As a result, _{x 0} is also determined from Equation (4). Constant d, f, h, and substituting x ₀ in equation (2), the relational expression between x _i and i is guided, with the derivation of this equation, calculating the pupil projection center position in the step S780 of FIG. 7 The expression is specified.

  The camera 1 according to the first embodiment described above acquires the pupil projection center positions for the number of samplings by pattern matching, and specifies an arithmetic expression for the pupil projection center positions based on the acquired positions, thereby determining all pupil projection center positions. Can be calculated. Therefore, it is possible to precisely specify the position of a pixel that receives a light beam that passes through the photographing optical system and enters the center of the microlens, and the effect of improving the accuracy of image synthesis and focus detection and focus adjustment. Play.

--- Second Embodiment ---
In the first embodiment in which the imaging apparatus according to the present invention is applied to a camera, the template images shown in FIGS. 6A to 6C recorded in advance in the built-in memory 130 in step S740 shown in FIG. A suitable one corresponding to the pupil diameter is selected. However, for example, when the options of the template image are not limited, or when the photographing optical system attribute information cannot be acquired in Step S730 because the lens barrel 15 does not have the photographing optical system control unit 150, in Step S740, It is necessary to generate a suitable template image corresponding to the pupil diameter. A second embodiment in which the imaging apparatus according to the present invention is applied to a camera when the photographing optical system attribute information cannot be acquired in step S730 will be described with reference to FIG.

  FIG. 9 is a flowchart showing the details of the pupil center projection position determination executed by the main control unit 100 in step S210 in FIGS. 2 (a) and 2 (b). Steps common to those in FIG. 7 are given the same reference numerals. Here, the steps given different symbols will be mainly described.

  In step S910, since the photographing optical system attribute information is not obtained and a suitable template image corresponding to the pupil diameter cannot be generated, a temporary template based on a predetermined provisional pupil diameter value is created. In step S920, pattern matching similar to that in step S750 is performed, and in step S930, a correlation value is calculated. For example, if a pattern is detected in which the correlation value rises and falls after the threshold value is exceeded, the contour of the pupil projection image 125 is detected, and the provisional pupil projection center position in the pupil projection image 125 is calculated. be able to. Next, a temporary template is created by changing the pupil diameter around the temporary pupil projection center position, and the correlation value is calculated again. If a pattern that rises after the correlation value rises and exceeds the threshold and then turns down is detected, the provisional pupil diameter in the projected image 125 of the pupil can be calculated assuming that the contour of the projected image 125 of the pupil is detected. In step S940, the above process is repeated, and a probable pupil diameter and pupil projection center position can be calculated when the correlation value exceeds a predetermined threshold. In step S950, a suitable template image corresponding to the pupil diameter is generated.

  The camera 1 according to the second embodiment described above has the same effects as the camera 1 according to the first embodiment even when the lens barrel 15 that cannot output the photographing optical system attribute information is used.

--- Third embodiment ---
In the first embodiment in which the imaging apparatus according to the present invention is applied to a camera, the pupil projection center position is recorded in the built-in memory 130 in step S790 shown in FIG. In this case, for example, when the pupil position h changes due to the focus adjustment of the photographing lens 160 or the replacement of the lens barrel 15, the correction amount of the pupil projection center position is set based on the recorded pupil projection center position. By calculating, all pupil projection center positions may be calculated. A third embodiment in which the imaging apparatus according to the present invention is applied to a camera will be described with reference to FIG.

  FIG. 10 is a flowchart showing details of the pupil center projection position determination executed by the main control unit 100 in step S210 in FIGS. 2 (a) and 2 (b). Steps common to those in FIG. 7 are given the same reference numerals. Here, the steps given different symbols will be mainly described.

In step S1010, a calculation formula for the correction amount of the pupil projection center position, which will be described later, is specified. In step S1020, the pupil projection center position in the case where h = h ₀ recorded in the built-in memory 130 is acquired. Through the calculation described later using these, all pupil projection center positions are determined and recorded in the built-in memory 130 in step S1030.

The specification of the calculation formula for the correction amount of the pupil projection center position in step S1010 shown in FIG. 10 will be described. In the formula (1), the value of the pupil-projection center position _{x i} with respect to the pupil position h When _x i {h}, pupil projection center position when the pupil position is h = _{h 0} is _x i _{{h 0}} expressed. The correction amount of the pupil projection center position is expressed as in Expression (5) when x _i {h} and x _i {h ₀ } are used and Expression (1) is considered.

Therefore, the arithmetic expression of all pupil projection center positions in step S1030 shown in FIG. 10 is specified as Expression (6).

  The camera 1 according to the third embodiment described above exhibits the same operational effects as the camera 1 according to the first embodiment with a small amount of calculation without using pattern matching.

--- Fourth embodiment ---
In the first to third embodiments in which the imaging device according to the present invention is applied to a camera, the main control unit 100 included in the camera body 10 of the camera 1 performs focus detection and focus adjustment or image synthesis of the photographing lens 160, and pupil center projection. Positioning. However, the image synthesis and the determination of the pupil center projection position may be executed by obtaining necessary information from the camera 1 by a PC (personal computer) operating in accordance with an image analysis computer program, for example. A fourth embodiment applied to a PC in which an image analysis computer program according to the present invention is installed will be described with reference to FIGS.

  FIG. 11 is a diagram showing a connection configuration between the PC 2 and the camera 1 according to the present embodiment. The PC 2 and the camera 1 are connected by communication. The connection form may be either a wireless connection or a wired connection. The image analysis computer program according to the present invention is installed in the PC 2 by the recording medium 3.

  The PC 2 according to the present embodiment determines the pupil center projection position in step S210 in FIG. 2B according to the image analysis computer program, and based on this, performs image synthesis in step S230. FIG. 12 is a flowchart showing details of pupil center projection position determination executed by the PC 2 according to the present embodiment in accordance with the image analysis computer program. Steps common to those in FIG. 7 are given the same reference numerals. Here, the steps given different symbols will be mainly described.

  In step S1310, subject imaging data is input from the camera 1 through communication. Through the edge extraction in step S720, photographing optical system attribute information is input from the camera 1 through communication in step S1330. Thereafter, the same processing as in FIG. 7 is executed.

  The camera 1 according to the above-described fourth embodiment has the same operational effects as the camera 1 according to the first embodiment without consuming the arithmetic processing performance of the main control unit 100 of the camera 1. Since image processing with higher functionality is possible, convenience is high.

---- Modified example ---
In the above-described first embodiment of the present invention, the edge extraction processing is performed by differential filter processing such as Laplacian. However, the imaging data including high-frequency components in which the subject has a fine pattern is used. On the other hand, it may be performed after pre-processing with a low-pass filter.

  The above-described embodiments and modifications may be combined. As long as the characteristic functions of the present invention are not impaired, the present invention is not limited to the device configuration in the above-described embodiment.

1 Camera 2 PC
3 recording medium 10 camera body 15 lens barrel 100 main control unit 110 image sensor 115 imaging pixel 120 microlens array 130 built-in memory 140 memory card 150 photographing optical system control unit 160 photographing lens 170 lens barrel memory

Claims (10)

A microlens array in which a plurality of microlenses are arranged;
A light receiving element array in which a plurality of light receiving elements that receive a light beam from an optical system through the micro lens array and output a light receiving signal are arranged;
Image generating means for generating a first image including an image corresponding to an outline of the plurality of microlenses based on the light reception signals obtained by the plurality of light receiving elements;
An imaging apparatus comprising: an arithmetic unit that obtains a position of an image that matches a second image corresponding to a contour of the microlens among the first image. The imaging device according to claim 1,
The calculation means obtains a position of an image that matches the second image for a first portion of the first image corresponding to the first microlens of the plurality of microlenses, and is different from the second microlens. For the second portion corresponding to the second microlens, the position of the image corresponding to the second image is obtained based on the arrangement of the plurality of microlenses and the position of the image corresponding to the second image. An imaging device. The imaging device according to claim 1 or 2,
2. The imaging apparatus according to claim 1, wherein the second image is generated based on a pupil diameter of the optical system. The imaging device according to any one of claims 1 to 3,
Storage means for storing, as a reference position, the position of an image that coincides with the second image when the position of the pupil of the optical system is a predetermined value;
The image pickup apparatus, wherein the calculation unit corrects a position of an image that matches the second image when a position of a pupil of the optical system is a value different from the predetermined value. The imaging apparatus according to claim 4,
When the pupil position of the optical system is different from the predetermined value, the arithmetic means corrects the position of the image that matches the second image based on the difference between the different value and the predetermined value. An imaging apparatus characterized by: In the imaging device according to any one of claims 1 to 5,
For each of the plurality of microlenses, a part of the light receiving elements is selected from the plurality of light receiving elements based on the position of the image that matches the second image, and an object is output using the output of the part of the light receiving elements. An image pickup apparatus, further comprising image combining means for combining image data of images. In the imaging device according to any one of claims 1 to 5,
Based on the position of the image that coincides with the second image, a pair of light receiving elements in which a pair of images are formed by a pair of the light beams passing through a pair of different pupils of the optical system, An image pickup apparatus, further comprising: a focus detection unit that selects each of the plurality of light receiving elements and detects a focus adjustment state of the optical system using outputs of the pair of light receiving elements. The imaging device according to claim 1,
The image generation means updates the value of the pupil diameter of the optical system based on the correlation between the provisional second image and the first image when the pupil diameter value of the optical system is a provisional value. An image pickup apparatus that updates to a value and generates the provisional second image when the value of the pupil diameter of the optical system is an update value. An image analysis computer program used for image analysis on captured image data generated in an imaging apparatus including a microlens array in which a plurality of microlenses are arranged and a light receiving element array in which a plurality of light receiving elements are arranged,
A generation instruction for generating first image data including an image corresponding to an outline of the plurality of microlenses based on light reception signals obtained by the plurality of light receiving elements;
An image analysis computer program comprising: a calculation instruction for obtaining a position of an image corresponding to a second image corresponding to a contour of the microlens among the first image. The image analysis computer program according to claim 9,
According to the calculation instruction, a position of an image corresponding to the second image is obtained for a first portion of the first image corresponding to the first microlens of the plurality of microlenses, and is different from the second microlens. For the second portion corresponding to the second microlens, the position of the image corresponding to the second image is obtained based on the arrangement of the plurality of microlenses and the position of the image corresponding to the second image. An image analysis computer program.

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